1. Field of the Disclosure
The present disclosure generally relates to micro-fluid ejection devices and, more particularly, to a micro-fluid ejection head having hydrophobic nozzle plate.
2. Description of the Related Art
The degree of hydrophobicity/hydrophilicity of a micro-fluid ejection head plays an important role in the overall performance of a micro-fluid ejection device. For example, as the size of the nozzles in the nozzle plate shrinks in order to get smaller droplet sizes, the sensitivity of the fluid ejected to the surface energy of the nozzle plate increases dramatically. One factor that contributes to this phenomenon is the accumulation of fluid or other contaminants on the nozzle plate surface. Such accumulation of fluid on the nozzle plate may adversely affect both the size and placement accuracy of the fluid droplets ejected from the ejection head. Therefore, the nozzle plate surface should be made hydrophobic to prevent the accumulation of fluids or other contaminants thereon.
The micro-fluid ejection head may be provided with a dual layer hydrophobic photoimageable nozzle plate (hPINP). Such micro-fluid ejection head may be manufactured by laminating a pre-formed dual layer photoresist film including a hydrophobic layer and a non-hydrophobic layer to a microfluid-ejection head structure with the non-hydrophobic layer being an attaching layer and the hydrophobic layer being an outer layer. The laminated dual layer photoresist film is then exposed and developed to provide nozzle holes. A single layer non-hydrophobic photoresist material may be deposited to the micro-fluid ejection head structure and then coated with hydrophobic resin layer. The single layer non-hydrophobic photoresist material and the hydrophobic resin layer may be simultaneously exposed or have a separate exposure step, and are then simultaneously developed to provide nozzle holes and form the dual layer hPINP. However, this type of dual layer hPINP manufactured either through liquid formulation or wafer level processed dry film laminates possess material incompatibility issues which inherently may lead to phase or layer separation.
A fabricated micro-fluid ejection head having a nozzle plate with non-hydrophobic surface may also be made hydrophobic through vapor deposition or spray coating of a hydrophobic resin layer. The extra post-nozzle-formation processing step required to generate the hydrophobic layer on the nozzle plate surface exposes the micro-fluid ejection head to significant threat of device contamination. Furthermore, the formed hydrophobic layer may lack good mechanical properties, and the hydrophobic characteristic of the nozzle plate may not be sustained for an extended period of time.
Thus, there is a need for hPINP with both improved mechanical properties and stable hydrophobic properties.